Bacterial diversity loss weakens community functional stability

Soil microbial communities are vital for maintaining soil health and function. Besides studying the composition and interactions of soil microbial communities, the focus has shifted towards using sequencing technologies to explore the diversity and functional potential of microbial communities in soil samples. Biodiversity tends to decrease slightly, and other microorganisms replace the lost microbial populations to maintain necessary functions. The microbial community oscillates within a stable ecological state, maintaining a dynamic equilibrium. However, it is not clear whether the loss of rhizosphere microbial communities diversity affects the stability of community functions under abiotic stress. In this study, we established microbial diversity using the gradient dilution method and investigated microbial community functions by introducing the exogenous phenolic acid autotoxic PHBA. The results of the study showed that reduced diversity of bacterial communities and increased plant autotoxicity led to poor plant growth, especially the aboveground of plants. We employed the natural connectivity topology parameter to reflect the bacterial community stability at different diversity levels. The results showed that dilution treatment and the addition of PHBA reduced the stability of the network. We described the resilience of microbial communities with bacterial diversity loss and PHBA addition using Bray-Curtis dissimilarity. Regardless of whether PHBA was added, the bacterial communities varied greatly in the initial stage. As PHBA was gradually degraded, the differences gradually decreased and eventually returned to the initial value. The dilution treatment groups were unable to fully recover, and the greater the dilution factor, the poorer the bacterial community's resilience. In the study of community function, we observed rapid degradation of PHBA at high diversity levels in the bacterial community. The initial concentration of PHBA is 200 mg/kg, and PHBA is almost completely degraded on the second day. As diversity decreased, the degradation rate of PHBA slowed down significantly, PHBA degradation was almost complete on the 4th day. However, under drought and salt stress, even in highly diverse communities, 33.84 % and 77.25 % of the PHBA were not completely degraded on the 6th day. The function of degrading PHBA can be disrupted due to the loss of community stability under stress conditions, especially drought stress. Even a slight decrease in micro